Alter Effect of Dense Heavy Rain and Lighting

All from today when i was playing L4D2 is that on “Hard Rain” and the Heavy Rain Effect and Reduced visibility that would occur time to time with almost realistic lighting was something I was thinking of throwing in my map.

I know L4D2 runs on a similar engine of Hl2 (Or same). Anyway to recreate that effect?

All from today when i was playing L4D2 is that on “Hard Rain” and the Heavy Rain Effect and Reduced visibility that would occur time to time with almost realistic lighting was something I was thinking of throwing in my map.

I know L4D2 runs on a similar engine of Hl2 (Or same). Anyway to recreate that effect?